Alkenylation palladium-catalyzed

Scheme 8.9. Palladium-Catalyzed Alkenylation of Aryl and Alkenyl Systems... 

Palladium-catalyzed alkenylation reactions involving pyrimidines can be achieved with hydrozirconated terminal alkynes, although the reaction is carried out in the presence of zinc chloride, so transmetallation to the zinc species is presumed to occur prior to the palladium-mediated coupling <1996ACS914, B-2002MI409>. Selective reaction at the 4-position of both 2,4-dichloropyrimidine and 2,4-dichloroquinazoline can be achieved. 

Palladium-Catalyzed Alkenylations and Arylations of Organometallic Compounds... 

The stereoselective synthesis of alkenes is basically a solved problem. Nowadays, all kinds of alkenes can be synthesized irrespective of whether their double bond is isolated or conjugated with another C=C double bond, a C=C triple bond, or an aromatic ring. This state of affairs is largely due to the discovery and the development of a number of palladium-catalyzed alkenylation and arylation reactions of organometallic compounds. 

Negishi E-I, Hu Q, Huang Z, Qian M, Wang G. Palladium-catalyzed alkenylation by the Negishi coupling. Aldrichimica Acta 2005 38 71-88. 

Huo, S., Negishi, E.-i. Palladium-catalyzed alkenyl-aryl, aryl-alkenyl, and alkenyl-alkenyl coupling reactions. Handbook of Organopalladium... 

Palladium-catalyzed alkenylation by the Negishi coupling , Negishi, E., Hu, Q., Huang, Z., Qian, M. and Wang, G., Aldrichimica Acta, 2005, 38,... 

III.2.6 Palladium-Catalyzed Alkenyl-Aryl, Aryl-Alkenyl, and Alkenyl-Alkenyl Coupling Reactions... 

Terminal alkenes can be used in a palladium-catalyzed alkenylation reaction of pyridine, pyrazine, quinoxaline, and pyridazine N-oxides 109 as reported by Chang (Scheme 53) (2008JA9254). This approach delivers regioselective C2-alkenylation products 110 and requires silver carbonate in a superstoichiometric amount as external oxidant. 

H. (1981) Palladium-catalyzed alkenylation of aromatic heterocycles with olefins. Synthesis of functionalized aromatic heterocycles. J. Org. Chem., 46, 851-5. 

Cross-Coupling Reactions with C(sp )-Electrophiles Palladium-catalyzed alkenylation reactions using alkenylzincs are very useful transformations that have been vastly investigated [8, 167, 168]. Aryl, heteroaryl, and alkenyl electrophiles can be used, but cross-coupling reactions with alkenyl electrophiles are particularly valuable, as this strategy provides one of the most generally applicable and satisfactory... 

In the total synthesis of the marine terpenoid (-)-frondosin B, Trauner and Hughes described an intramolecular palladium-catalyzed alkenylation reaction between a benzofuran and an enol triflate (124 to 125, Scheme 10.41). Although the mechanism to form the key seven-membered ring is still unclear, a reasonable hypothesis would involve oxidative addition of palladium(0) to the C—OTf bond, C3-palladation of the benzofuran and reductive elimination to form the new C—C bond. This work is notable as it was the first example of heteroaromatic C—H activation in a complex molecule setting. 

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